title: Tryptophan-kynurenine metabolism and insulin resistance in hepatitis C patients.
abstract: Chronic hepatitis C virus (HCV) infection is associated with 50% incidence of insulin resistance (IR) that is fourfold higher than that in non-HCV population. IR impairs the outcome of antiviral treatment. The molecular mechanisms of IR in HCV are not entirely clear. Experimental and clinical data suggested that hepatitis C virus per se is diabetogenic. However, presence of HCV alone does not affect IR. It was proposed that IR is mediated by proinflammatory cytokines, mainly by TNF-alpha. TNF-alpha potentiates interferon-gamma-induced transcriptional activation of indoleamine 2,3-dioxygenase, the rate-limiting enzyme of tryptophan- (TRP-) kynurenine (KYN) metabolism. Upregulation of TRP-KYN metabolism was reported in HCV patients. KYN and some of its derivatives affect insulin signaling pathways. We hypothesized that upregulation of TRP-KYN metabolism might contribute to the development of IR in HCV. To check this suggestion, we evaluated serum concentrations of TRP and KYN and HOMA-IR and HOMA-beta in 60 chronic HCV patients considered for the treatment with IFN-alpha. KYN and TRP concentrations correlated with HOMA-IR and HOMA-beta scores. Our data suggest the involvement of KYN and its metabolites in the development of IR in HCV patients. TRP-KYN metabolism might be a new target for prevention and treatment of IR in HCV patients.
authors.affiliation: Psychiatry and Inflammation Program, Department of Psychiatry, Tufts Medical Center, Tufts University, Boston, MA 02111, USA.
authors.forename: G F
authors.initials: GF
authors.lastname: Oxenkrug
authors.forename: W A
authors.initials: WA
authors.lastname: Turski
authors.forename: W
authors.initials: W
authors.lastname: Zgrajka
authors.forename: J V
authors.initials: JV
authors.lastname: Weinstock
authors.forename: P
authors.initials: P
authors.lastname: Summergrad